Surface Roughness Parameters Research Articles

Dry milling of stir-cast and heat-treated EV31A magnesium alloy: An experimental investigation based on the multi-criteria optimization method

The purpose of this study is to examine the impact of various milling parameters and sample preparation methods on the end-milling of EV31A Mg alloy under as-cast, T4, and T6 heat-treated conditions. The test specimens were prepared through stir-casting and heat-treated according to T4 and T6 conditions. The CNC vertical milling machine with the HSS tool was used for the end-milling process based on Taguchi's L9 orthogonal array. Three levels of variation are applied to the process parameters, including spindle speed (S), feed rate (f), depth of cut (d), and test specimen (as-cast, T4, and T6 EV31A). The parameters of surface roughness (Ra, Rz, Sa, Sz), the rate of material removal (MRR), and the cutting force (Fr) were similarly measured. For surface roughness, optical profilometry was used, while the weight loss method and dynamometer were employed, respectively, to assess MRR and Fr. In order to improve the process parameters, TOPSIS (techniques order preferences by similarity to ideal solution) is employed. This method reduces several responses to a single measurable response (the closeness coefficient). S = 1500 rpm, f = 150 mm/min, and aP = 1.5 mm are the ideal process parameters to achieve the maximum closeness coefficient (Ci) of 0. 917129 under as-cast circumstances. Furthermore, analysis of variance (ANOVA) verifies that sample preparation methods of 24.59 % and depth of cut of 38.19 % significantly impact response characteristics.

Influence of Novel Al-Ni Electrodes on Roughness and Machining Time in Inconel 625 EDM Machining: A Comprehensive RSM Performance Analysis

In the context of Inconel 625 machining, this study explores the effects of novel Al-Ni nano electrodes on surface roughness and machining time. Thorough performance study was undertaken to clarify the complex connections between the machining settings, electrode composition, and final surface quality. Important insights were obtained via methodical experimentation and data analysis, which helps optimize the machining procedures for improved productivity and surface quality when milling Inconel 625. This research presents an experimental investigation of the effects of the Electric Discharge Machining (EDM) input parameters, namely current, pulse-on time, and pulse-off time, on the surface roughness and machining time output parameters. Inconel 625 was the material of choice for the work piece. Electric discharge machining oil was used as the dielectric fluid and aluminium nanocomposite as the tool electrode. Response surface methodology (RSM) approach was employed in the experimentation. ANOVA was used to optimize the parameters and obtain the lowest possible surface roughness (SR) and machining time. The findings show that pulse-off time is the most significant motivating factor for SR. The current is the main determining factor for machining time. The Central Composite Design approach was used for optimization.

Electrochemical 3-D morphology based degradation quantification framework for lithium-ion battery under low temperature

In high-latitude areas, lithium-ion batteries for electric vehicles frequently operate under low-temperature conditions. However, lithium-ion battery suffers from complex energy loss and performance degradation under low temperature. In order to quantify the degradation mode of the battery, this paper proposes a framework with electrochemical theory and electrode 3-D morphology. The proposed framework mainly includes two parts: Firstly, the degradation modes (DMs) of the battery are extracted from incremental capacity (IC), differential voltage (DV) techniques and electrochemical impedance spectroscopy (EIS). Secondly, the 3-dimension (3-D) morphological calculation method is proposed to analyze the degradation situation of the battery electrodes. Then, the battery aging and performance testing system under low temperature is established to verify the effectiveness of the proposed framework from the perspective of surface morphology. In order to validate the effectiveness of the proposed framework, an experimental bench for battery low-temperature aging and performance testing is constructed. The experimental results demonstrate that: (1) Battery capacity is greatly reduced at low temperatures, and loss of lithium inventory (LLI) is greater at low temperatures (−5 °C and −10 °C) than at 25 °C under the same state of health (SOH). (2) By analyzing 3-D morphology, the low temperature can lead to a significant change in the surface roughness parameters of the anode electrode. The low temperature aggravates the reduction of anode gap area. It is found that the microscopic mesomorphic changes are closely related to the aging of the battery. (3) The anode graphite (002) peak position is shifted to a low angle of 2.2° under low temperature. Scanning electron microscope (SEM) images shows the graphite anode is covered by a lithium-rich SEI at low temperature. (4) Post-test calculations of the consistency of the relevant covariates revealed that the electrochemical and morphological covariates are highly linearly correlated, respectively. Hence, the effectiveness of the proposed framework is verified and a novel perspective is provided to reveal the battery performance degradation under low temperatures, which can help guarantee safe operation through battery management system.

Characterization of the microstructure evolution features of various aggregates based on confocal laser scanning microscope

To reveal the microscale structural evolution characteristics of aggregates, this study employs confocal laser scanning microscope (CLSM) to conduct the surface microstructures of six aggregates: limestone, basalt, granite, diabase, sandstone, and recycled aggregate (RA). Quantitative analysis was performed on the surface morphology, roughness parameters, and material ratio of the aggregates. The results indicate that the surface features of the aggregates vary with the type and treatment method, and these distinctions may be attributed to variations in diagenetic conditions. In the original state, the surface texture of limestone, basalt, and diabase is relatively minimal, with arithmetic mean height (Ra) distributed between 1.4 μm and 3.5 μm. Conversely, the surface texture of granite, sandstone, and RA is more complex, with Ra distributed between 7.5 μm and 9.5 μm. The roughness indices of basalt, limestone, and diabase show an increasing trend after lime treatment, indicating a more pronounced presence of microscopic peaks and pits. In contrast, all roughness indices of granite, sandstone, and RA exhibit a declining after lime treatment. After polishing, the Ra of the surfaces of the six different aggregates shows varying degrees of reduction. Specifically, Ra decreased by 43.89%, 33.11%, 26.52%, 30.14%, 29.80%, and 38.79% for limestone, basalt, granite, diabase, sandstone, and RA, respectively. Furthermore, the height distribution frequency and material ratio of aggregate surfaces vary with the type and treatment of aggregates. Through grey correlation analysis, the correlation degrees of root mean square slope (Rdq), kurtosis (Rku), and surface texture aspect ratio (Rtr) are 0.9524, 0.9522, and 0.9514, respectively, belonging to hybrid parameter, height parameter, and spatial parameter. This suggests a close relationship between these parameters and the polished stone value (PSV) of the aggregates. These findings offer valuable insights for improving aggregate selection and treatment processes, potentially leading to enhanced durability and performance of construction materials.

Optimization of µ-WEDM Parameters for MRR and SR on Ti-6Al-4V

Micro EDM is unconventional metal removing technique that is effective in machining hard-to-cut conductive materials. It has a big potential in modifying surfaces of metallic bone implants for better biocompatibility by providing proper surface topography to ease cell adhesion. However, it is still important to study machining performance. This paper investigates material removal rate (MRR) and surface roughness (SR) of micro WEDM on Ti-6Al-4V alloy. Three level Taguchi’s design was implemented to observe the effect of capacitance and gap voltage. Moreover, analysis of variance (ANOVA) and grey relation analysis (GRA) allowed to investigate contribution of each parameter and find their best combination for multiple output optimization. Results showed that highest MRR of 1.72*10-2 mm3/s can be achieved at 10 nF and 90 V values, while smallest SR of 0.309 µm can be achieved at 1nF and 90 V. In addition, the contribution and significance of capacitance on MRR and SR was considerably higher than the effect of gap voltage. Lastly, the optimal parameters for multiple output performance were calculated at 10 nF and 90 V values.

Enhancing Machining performance in Stainless Steel Machining using MXene Coolant: A Detailed Examination

Metal cutting, a complex process in manufacturing, involves various factors that significantly affect the quality of the final product. Notably, the turning process is crucial, with outcomes that heavily depend on multiple machining parameters. These parameters encompass speed, depth of cut, feed rate, the type of coolant used (specifically, high heat transfer MXene coolant), and insert types, among others. The material of the workpiece is also a critical factor in the metal-cutting operation. This study focuses on achieving optimal surface quality and minimizing cutting forces in the turning process. It recognizes the substantial impact of numerous process parameters, directly or indirectly affecting the product's surface roughness and cutting forces. Understanding these optimal parameters can lower machining costs and improve product quality. Our research concentrates on turning a stainless-steel alloy workpiece using a carbide insert tool. We employ the Response Surface Method (RSM) to optimize cutting parameters within a set range of cutting speed (100, 125, 150 m/min), feed rate (0.1, 0.2, 0.3 mm/rev), and depth of cut (0.4, 0.8, 1.2 mm). Additionally, we use various tool geometries and the RSM design of experiments to enhance and analyze the multi-response parameters of surface roughness and tool life. Optimal machining parameters for MXene-NFC involve a cutting speed of 140 m/min, a feed rate of 0.05 mm/rev, and a depth of cut of 0.5 mm. These settings ensure minimal surface roughness, maximum tool life, and the greatest total length of cut, achieving a composite desirability of 0.695.

Tailoring the structural, morphological, surface wettability and hardness features of Makrofol HS for surface applications: effect of DBD treatment

ABSTRACT In current research, Makrofol HS polymeric films have been utilized to evaluate the alterations in the surface properties under an atmospheric-pressure dielectric barrier discharge (DBD) plasma source. Upon DBD plasma exposure with various exposure durations ranging from 10 min to 120 min, the structural, surface wettability, surface free energy, surface roughness, and hardness features of Makrofol HS films have been studied and analyzed using different techniques. The FTIR spectra demonstrated that small changes in the band intensities correspond to the C-O-C as well as C=O bonds. Further, the changes in the absorption bands are correlated to the treatment time, leading to two critical processes, degradation, and crosslinking. The results of surface wettability displayed that the liquids' contact angle decreased from 84 ± 3o, 77 ± 3o and 62 ± 2o for water, glycerol, and dimethyl to 45 ± 1o, 42 ± 1o, and 36 ± 1o for untreated and treated samples at the highest treatment time, respectively. Also, the surface free energy significantly amended with increasing plasma exposure time. This modification in the treated surface indicates the increase in the polar groups on the treated surfaces, which then become hydrophilic surfaces. The samples' surface roughness parameters Ra, Rq, and Rz increased from 0.057 ± 0.003, 0.084 ± 0.004 and 0.366 ± 0.02 mm for untreated samples to 1.463 ± 0.073, 1.707 ± 0.085, and 6.839 ± 0.34 mm for treated samples at the highest treatment time, respectively. The Vickers hardness measurements showed an increase in the Vickers hardness from 12.31 ± 0.61 kgf/mm2 for the untreated sample to 44.89 ± 2.24 kgf/mm2 for the treated sample at the highest duration.

Optimization of Surface Roughness of Aluminium RSA 443 in Diamond Tool Turning

Context—Rapidly solidified aluminium alloy (RSA 443) is increasingly used in the manufacturing of optical mold inserts because of its fine nanostructure, relatively low cost, excellent thermal properties, and high hardness. However, RSA 443 is challenging for single-point diamond machining because the high silicon content mitigates against good surface finishes. Objectives—The objectives were to investigate multiple different ways to optimize the process parameters for optimal surface roughness on diamond-turned aluminium alloy RSA 443. The response surface equation was used as input to three different artificial intelligence tools, namely genetic algorithm (GA), particle swarm optimization (PSO), and differential evolution (DE), which were then compared. Results—The surface roughness machinability of RSA443 in single-point diamond turning was primarily determined by cutting speed, and secondly, cutting feed rate, with cutting depth being less important. The optimal conditions for the best surface finish Ra = 14.02 nm were found to be at the maximum rotational speed of 3000 rpm, cutting feed rate of 4.84 mm/min, and depth of cut of 14.52 µm with optimizing error of 3.2%. Regarding optimization techniques, the genetic algorithm performed best, then differential evolution, and finally particle swarm optimization. Originality—The study determines optimal diamond machining parameters for RSA 443, and identifies the superiority of GA above PSO and DE as optimization methods. The principles have the potential to be applied to other materials (e.g., in the RSA family) and machining processes (e.g., turning, milling).

Modeling and Optimization of Turning Hastelloy C-276 under Sustainable Machining Environments

Due to their numerous applications in the aerospace, chemical, and nuclear power industries, environmentally responsible superalloy machining is a major problem in the current production environment. Additionally, Ni-based superalloys are regarded as difficult to manufacture because of their great strength under hot and chemically reactive settings. Therefore, it is necessary to machine these materials using adequate cooling and lubricating solutions. Current study has been based on the optimisation and modelling of turning Hastelloy C-276 under dry, flood, and least lubrication system. A Taguchi L-9 arrangement was used as plan of experiment and modeling was enabled through ANOVA, regression analysis and Taguchi optimization. The results depicted optimal parameters for surface roughness and temperature at v2-f1-d1-CE3 and v1-f2-d1-CE3. Likewise, for CRC and shear angle the best combination was observed at v3-f3-d2-CE2. From ANOVA analysis, the benefaction of C.E, depth of cut and feed rate on S.R been listed as 46.70%, 40.44% and 10.66%. Likewise, for temperature cutting speed has benefaction of (53.09%), cooling environment (23.94%), depth of cut (6.10%) and feed rate 5.49% . In similar fashion, CRC and Shear angle were influenced by feed rate and cutting speed having contribution of 62.89% and 5.15% respectively. Furthermore, minimum standard error between the fitted and observed values for S.R., temperature, CRC, and shear angle were calculated as 0.0149, 7.66, 0.267, and 1.80 units. Finally, the marginal reduction of cutting temperature and surface roughness through utilization of MQL implies the sustainable machining conditions.

Determination and prediction of surface and kerf properties in abrasive water jet machining of Fe-Cr-C based hardfacing wear plates

Improving and maintaining the sustainability, profitability and efficiency of sectors such as manufacturing, mining and agriculture are the most important goals for industries. It is therefore quite common to apply hardfacing method to products and equipment created to achieve these goals. However, machining of the workpiece is necessary to ensure dimensional accuracy as a result of hardfacing production. In the processing of hardfacing materials with traditional machining methods, negative factors such as tool wear and thermal effects occur. For this reason, the cutting performance of hardfacing wear plate with abrasive water jet, which is one of the unconventional manufacturing processes, was investigated in this study. Tests were realized in regard to the full factorial experimental design, which includes the changes in the levels of material alignment direction, abrasive mass flow rate and traverse speed parameters. The influences of the test parameters on the surface roughness and kerf taper angle constituting the cutting performance were determined by analysis of variance (ANOVA). In addition, the effects of changes in parameter levels were investigated. Material alignment direction was found to be the most effective test parameter for surface roughness and kerf taper angle. The influences of parameter and parameter levels on the formation of surface conditions were determined with surface images. Thus, machining mechanisms and surface morphologies were explained by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Optimal levels of test parameters were achieved by performing multiple-response optimization with equal importance. Finally, the estimated results of cutting performances were found by general linear model, and all results were confirmed by regression analysis.

Hydraulic properties of stressed granite fractures with heat-induced void alteration

During the extraction of geothermal heat, the changes in temperature and pressure environments can alter the mechanical and hydraulic behavior of fractured rock masses, affecting the overall transmissivity and heat extraction efficiency accordingly. This study carried out a series of experiments, including X-ray diffraction (XRD), scanning electron microscope (SEM), uniaxial compression tests, and surface morphological scanning, to explore the influence of reservoir temperature on the mechanical behavior of granite and fracture surface topography. The results indicate that as the temperature increases, the uniaxial compressive strength, elastic modulus, and Poisson's ratio of granite show similar variation patterns that increase as the temperature approaches 200 °C and then decrease. In addition, with the increase in temperature, the overall surface elevation and roughness parameters generally decrease due to surface asperity degradation, with the maximum mean mechanical aperture found at 200 °C. Flow simulations were conducted to further explore the influence of temperature and pressure environments on fracture transmissivity and flow fields. It is found that the normalized equivalent hydraulic aperture BN of the tested fractures decreases progressively as the stress increases, and more scattered distributions of BN are observed under higher compressive stresses. Moreover, with the continuous increase in temperature, the average BN slowly increases to its peak of ~0.78 at 200 °C, then it decreases to ~0.76 at 300 °C and remains nearly constant. These findings can be important for assessing heat production performances during the geothermal extraction process with spatially and temporally varying reservoir temperatures and pressures.

A Hybrid Electrochemical Magnetorheological Finishing Process for Surface Enhancement of Biomedical Implants

Abstract The proposed novel polishing method, hybrid electrochemical magnetorheological (H-ECMR) finishing, combines electrochemical reactions and mechanical abrasion on the workpiece surface to reduce finishing time. Moreover, H-ECMR finishing on the biomaterial surface produces a uniform, thick passive oxide layer to improve corrosion resistance. Herein, the electrolytic solution facilitates the chemical reaction and acts as a carrier medium for carbonyl iron particles (CIPs) in magnetorheological (MR) fluid. The synergic action of the two processes reduces the surface finishing time, which takes longer in the case of the conventional magnetorheological Finishing (MRF) process, as observed experimentally. The developed H-ECMR finishing process employs an electromagnet, maneuvering in situ surface quality variation by altering the magnetic field during finishing. The magnetic shield material (i.e., mu-metal) confines the bottom of the electromagnet core to restrict the magnetic field's leakage and provide a uniform and concentrated magnetic field at the polishing spot. The effectiveness of the H-ECMR process is evaluated based on various surface roughness parameters (i.e., average surface roughness (Ra), skewness (Rsk), and kurtosis (Rku)) and compared with the MRF process. A 96.4% reduction in Ra value is attained in the H-ECMR polishing compared to 49.6% in MRF for identical polishing time. Furthermore, an analytical model is developed to evaluate the final Ra attained from the developed H-ECMR polishing process and agrees well with the experimental results. The impact of different process parameters on surface roughness values is also analyzed. The electrochemical reaction forms a thick and unvarying passive layer on the Ti–6Al–4V surface as layer thickness increases to 78 nm from 8 nm. A case study on the femoral head of the Total Hip Arthroplasty (THA) for enhancement in the surface roughness and biocompatibility is performed through the developed H-ECMR polishing. The Ra value is decreased to 21.3 nm from 326 nm on the femoral head surface through the contour-parallel radial toolpath strategy.

Preprocessing method for robust topography reconstruction of surfaces of metal additive manufactured parts based on focus variation microscopy

Abstract When using an areal measuring optical instrument to measure rough surfaces, especially surfaces generated by metal additive manufacturing (e.g. laser and electron beam powder bed fusion), topographical artifacts such as spikes on a reconstructed surface are nearly unavoidable. These artifacts may affect the determination of surface roughness parameters and lead to erroneous surface features. This paper proposes a new preprocessing method to eliminate most artifacts before extracting surface heights of rough surfaces measured by focus variation microscopy. In this method, the axial region where a surface height value is located with the highest probability is estimated, based on datasets of planes parallel to the axial scanning direction. Results regarding height measurements with and without the preprocessing method are compared by measuring a Rubert Microsurf 329 comparator test panel for reference and workpieces produced by metal additive manufacturing.

Multi-objective modeling and evaluation for energy saving and high efficiency production oriented multidirectional turning considering energy, efficiency, economy and quality

To promote energy saving, high efficiency and quality production in the mechanical manufacturing industry, a large number of studies have been conducted on modelling and evaluation. However, most of the approaches have focused on single objective modelling, evaluation and conventional machining method like unidirectional turning (UDT). This paper presents a multi-objective modelling and evaluation method for energy, efficiency, economy and quality using a new process of forward-and-reverse multidirectional turning (MDT). Firstly, the multi-objective influential factors of cutting parameters for energy consumption, cutting time, production cost and surface roughness of MDT are analyzed to establish the corresponding models, respectively. Then taking the energy consumption, cutting time, production cost and surface roughness as the objectives, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is applied for the multi-objective evaluation through different processes. Finally, the case study shows the practicability of the MDT method and evaluation method for energy optimization and energy conservation.

Study on gear contact stiffness and backlash of harmonic drive based on fractal theory

Contact stiffness and backlash in the harmonic drive significantly impact a robot's positioning accuracy and vibration characteristics. The height of the harmonic drive tooth pair is typically less than 1 mm, making the measurement and modeling of backlash and contact stiffness inherently complex. This paper proposes a contact stiffness and backlash model by establishing a correlation between fractal parameters and tooth contact load. To obtain the fractal roughness parameters of the real machined tooth surface, a combination of a noncontact optical profiler and the RMS method is employed. Subsequently, the study explores the influence of rough tooth surface and contact force fractal parameters on contact stiffness and gear backlash. The results demonstrate the substantial impact of surface topography parameters and contact force on contact stiffness and backlash. Specifically, an increase in the fractal dimension correlates with a reduction in gear backlash and contact stiffness. Conversely, the fractal roughness parameter exhibits the opposite effect. Notably, an increase in contact force enhances contact stiffness.

Multispecies colonisation and surface erosion on A106 GB industry-finished steel used in heat exchangers

Multispecies bacterial attachment to carbon steel surfaces is not fully understood; for example, as to why the attachment of certain bacteria influences corrosion. In this study, finished steel, A 106 GB was exposed to a mixed bacterial culture in a batch reactor system at a constant temperature of 35 °C to evaluate the corrosion rate with and without bacterial influence. Cultures collected from the cooling tower site were exposed to coupons and were grown in a batch reactor. Atomic force microscopy (AFM) was used to obtain roughness parameters. Surface morphology and colonisation patterns were observed by scanning electron microscopy (SEM). 16S rDNA sequencing indicated predominance of Pseudomonas sp. and Clostridium sp. on the rough surfaces. Cell colonisation of surfaces showed no time-related differences, with differences observed on surface roughness parameters. Intergranular and uniform corrosion was observed. The smooth finished steel surface performed best in resisting corrosion.

Diatom-induced impact on shear strength characteristics of fine-grained soils

Diatomaceous soils, composed of diatom microfossils with biological origins, have geotechnical properties that are fundamentally different from those of conventional non-diatomaceous fine-grained soils. Despite their high fines content, diatomaceous soils typically exhibit remarkably high shear resistance, approaching that of sandy soils. However, the exact role that diatoms play in controlling the mechanical properties of fine-grained soils and the underlying mechanisms remain unclear. In light of this, the shear strength response of diatomaceous soils was systematically investigated using consolidated undrained triaxial compression tests on diatom–kaolin mixtures (DKMs) with various diatom contents and overconsolidation ratios. The micro- and nano-scale structures of the soil samples were characterized in detail using scanning electron microscope (SEM) and atomic force microscope (AFM) to interpret the abnormal shear strength parameters of diatomaceous soils. The results indicated that the presence of diatoms could contribute to significantly higher strength, e.g. the friction angle of DKMs was improved by 72.7% to 37° and the value of undrained shear strength tripled with diatom content increasing from 20% to 100%. Such significant improvement in soil strength with diatom inclusion could be attribute to the hard siliceous skeleton of diatoms and the interlocking between particles with rough surfaces, which were quantitatively analyzed by the surface roughness parameters with AFM. Furthermore, a conceptual model established based on the macro-mechanical tests and microscopic observations portrays a microstructural evolution of soils with increasing diatoms. The microstructure of soils was gradually transformed from the matrix-type to the skeletal one, resulting in a continual augmentation in shear strength through mutual interactions between diatom microfossils. This paper provides new insights into the multi-scale structural properties of diatoms and significantly advances our understanding of the mechanical behavior of diatomaceous soils.

Carbon fiber paper based on composites of carbon and polyacrylonitrile for fuel cell application

Carbon fiber paper is one of the most important substrates used in the gas diffusion layer of the polymer electrolyte membrane fuel cell. A novel approach to creating carbon fiber paper using polyacrylonitrile compounds was proposed in this study. The technique incorporated varying amounts of carbon materials, including carbon black (Vulcan), graphite powder, and carbon nanotubes. Polyacrylonitrile carbon materials were prepared through the spinning process, followed by oxidative stabilization under an oxygen atmosphere at a temperature range of 160–300 °C as the first step. The pliable material undergoes a conversion process to create a compound or ladder that is non-plastic, which is then stabilized in an N2 atmosphere. The fibers are then pre-carbonized at temperatures ranging from 300 to 600 °C and further carbonized between 600 and 1100 °C. After that, Teflon is added and the resulting fibers are made into sheets during the production process. Finally, physical measurements and electrochemical methods such as: checking the amount of water absorption, scanning electron microscope (SEM), chronopotentiometry, electrochemical impedance spectroscopy, electron resistance of carbon sheet, double layer capacitance, and surface roughness parameter were evaluated. The results indicate that the best performance is related to CP7 carbon paper (with a 30–70 % combination of polyacrylonitrile and carbon black).

Effect of aging and bleaching on the color stability and surface roughness of a recently introduced single-shade composite resin

ObjectivesTo assess the effects of aging and bleaching procedures on the color stability and surface roughness of a new single-shade composite versus multi-shade composite resins. MethodsA single-shade composite resin (Charisma Diamond One, CDO) and 3 multi-shade composite resins (Tetric NCeram, Filtek Z350 XT, Clearfil Majesty Posterior) were tested. Thirty specimens of each material were subjected to one of the aging procedures respectively: immersion in distilled water (12 days/37 °C), immersion in coffee (12 days/37 °C), or water thermocycling (10,000 cycles/5–55 °C). All specimens underwent in-office bleaching after aging. Kruskal-Wallis tests and analysis of variance were used for statistical analysis (α=0.05). ResultsAll materials exhibited a change of color (ΔE00), translucency (RTP), whiteness (WID) and surface roughness parameters (Sa,Sv) after aging and bleaching procedures. CDO showed the highest ΔE00 among all resins with the highest RTP value, regardless of the aging procedures. Immersion in coffee led to the significantly highest ∆E00 values and lowest RTP values for nearly all resins. Positive ΔWID1 (WID(bleaching)−WID(baseline)) values were found in distilled water immersion and thermocycling groups, while negative ΔWID1 values were found in the coffee immersion group for all materials. Besides, positive ΔWID2 (WID(bleaching)−WID(aging)) values were found in all aging groups for nearly all materials. All materials showed an increasing trend in Sa and Sv after bleaching. ConclusionsCDO showed more pronounced discoloration than multi-shade composite resins. Although the whiteness of all resins increased after bleaching, none was completely restored in the coffee immersion group. Bleaching significantly increased the surface roughness of all materials. Clinical significanceCharisma Diamond One is more susceptible to discoloration, which may affect its long-term success rate. Bleaching could partially reduce the color change of the composite resins but did not return them completely to their original state. The roughness of the resins increased after bleaching, prompting dentists to repolish them after bleaching.

Research on the surface characteristics of 42CrMo alloy steel pulse electrochemical machining

Electrochemical processing, due to its unique material removal mechanism compared to mechanical processing, often results in significantly different micro-morphologies. It is widely used in areas such as aerospace component processing, surface finishing, passivation, micro-structure mold processing, etc. The complexity of alloy steel composition makes uniform etching difficult to achieve, and the post-etch micro-morphology is also complex, making it challenging to describe and analyze. Therefore, it is difficult to analyze the surface morphology of electrochemical etching under different parameters. In this study, a self-developed electrochemical etching device with adjustable DC voltage, pulse width voltage, and pulse width positive and negative voltage output was used. Different parameters of pulse voltage were used to etch the surface of 42CrMo alloy steel. Due to the strong relationship between surface roughness parameters and the chosen measurement scale, as well as the surface morphology and waviness errors introduced by specimen preparation and etching processes, a wavelet filtering method was used to remove the low frequency components in the surface morphology, and only the surface roughness part was retained for fractal parameter calculation and analysis. The research showed that fractal analysis can also be applied to analyze the surface morphology after electrochemical etching. Pulse voltages with characteristic voltages, characteristic pulse frequencies, and duty ratios can achieve better surface quality during positive pulse etching. Positive and negative pulse etching can obtain better surface morphology than positive pulse etching, but the etching amount is lower, making it suitable for precision finishing.